The H&K Mk24, minus the suppressor and laser aiming module.

The Mk24 is a .45 caliber handgun used by the United States military. An upgrade of Heckler and Koch’s Mk23, the Mk24 is the standard issue handgun for Marine Vent Infiltration Specialists, or “Vent Rats”, some of whom choose to carry it as a primary weapon when infiltrating ventilation systems, fitted with an optional suppressor. It is also an option for Special Forces operators; Mark Drake and Trevor Wierzbowski of the 9th Regiment’s Reconnaissance In Force Team 1 both carried Mk24s, although Drake eventually returned his in favor of a Zastava M88A he captured in Romania.

Weapon Designation:Pistol, .45 Caliber, Semiautomatic, Mk24
Place of Origin:Germany
In Service:2054-present
Production History:
Manufacturer:Heckler & Koch GmbH
Weight:2.43 lb (1.2 kg) (plain)
4.23 lb (2.02 kg) (with suppressor and LAM)
Length:9.65 in (245 mm) (plain)
16.5 in (421 mm) (with suppressor)
Barrel Length:5.87 in (149 mm)
Cartridge:.45 H&K
Action:Short recoil
Rate of Fire:Semiautomatic
Muzzle Velocity:1,600 ft/s (488 m/s) with M45120D round
1,000 ft/s (305 m/s) with M45200P round
Muzzle Energy:682 ft/lbs (924 Joules) with M45120D fluted round
444 ft/lbs (602 Joules) with M45200P fluted round
Effective Range:50 m (55 yd)
Feed System:12-round detachable box magazine
Sights:Iron sights


Although the United States Marine Corps liked the Mk23, in the 2050s they wanted an improved design to incorporate suggestions made by field users. Heckler and Koch’s answer was the similar Mk24, which was accepted by the US military as a whole in 2054.


The Mk24 is very similar to the Mk23. The primary change is the addition of an ambidextrous slide “block”. Although this block closely resembles an M1911-style thumb safety, the actual purpose of the slide block is not to prevent the weapon from firing, but to prevent the slide from cycling during firing. This helps to keep the weapon much quieter when fired with a suppressor, because there is no open ejection port for gas to escape, and because the spent casing is not ejected. This does, however, greatly limit the rate of fire, as after each shot, the slide block switch must be pushed into the downward position, the slide cycled by hand, and the slide block switch pressed up again. This also increases felt recoil significantly, because the slide does not recoil and therefore the recoil spring does not absorb any of the firing force.

Another improvement made to the Mk24 is the addition of an ammunition count display on the left side of the frame, in place of the decocking lever, which has been moved to the right side of the frame. Additionally, the Mk24 is intended for use with a smaller, lighter laser aiming module than the one built for the Mk23.

Although the Mk24 is capable of firing both .45 ACP and .45 Super, it is intended for use with the .45 H&K, which is nothing more than a variation on .45 Super with a slightly thicker casing. Although this results in lower internal capacity for propellant, advancements made in propellants allow the .45 H&K to be loaded in both a subsonic cartridge with similar performance to .45 ACP, and a supersonic cartridge similar to .45 Super. The subsonic round, which weighs 200 grains, is intended for use with the suppressor and has a maximum muzzle velocity of 305 meters/second. The supersonic round weighs 120 grains, has a maximum muzzle velocity of 488 meters/second, and is intended for use when the weapon is not being used with the suppressor, as the sonic boom from firing is less of an issue than when deliberately trying to be as silent as possible. However, it is entirely possible to fire the subsonic round without the suppressor or the supersonic round with it if necessary.

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